Metal organic framework derived mesoporous carbon nitrides with a high specific surface area and chromium oxide nanoparticles for CO2 and hydrogen adsorption

Abstract

In this work, we report a simple and versatile method for the preparation of mesoporous carbon nitrides (MCNs) functionalized with highly dispersed chromium oxide nanoparticles by using a metal organic framework, MIL-100(Cr), as a template and aminoguanidine hydrochloride (AG) as a high nitrogen content single molecular precursor. We are able to synthesise these metal oxide functionalized MCN materials with single step carbonization but without using any toxic template removal process using HF or NaOH. The absence of a washing procedure with toxic acid also allows the incorporation of a large amount of metal oxide particles inside the porous channels of MCNs. The obtained MCN materials exhibit a high specific surface area and a large pore volume. The AG to template ratios are varied to control the amine functional groups and the textural parameters including the specific surface area and pore volume. It is found that the AG to template ratio of 1.5 is the best condition to obtain MCNs with a specific surface area of 1294 m² g⁻¹, which is the highest value reported so far for MCN-based materials. FT-IR and XPS results reveal that the prepared materials contain free NH₂ groups within the CN network which help to anchor metal oxide nanoparticles and provide highly dispersed basic sites. These functionalized MCN materials are also used as adsorbents for CO₂ capture. Among the materials studied, the MCN with the highest specific surface area shows the largest CO₂ adsorption capacity (16.8 mmol g⁻¹) which is much higher than those of MCN materials prepared from SBA-15 and KIT-6, activated carbon, MIL-100(Cr), SBA-15, and multiwalled carbon nanotubes. This high adsorption capacity is mainly due to the strong synergistic effect between the MCN with high specific surface area and highly dispersed metal oxide nanoparticles.